A variety of kites are presently commercially available for recreational purposes or for the use by the serious competitor aiming to excel at competition kite-sailing. Depending on the design of a particular kite and the materials used to construct it, it may be flown in light or moderate winds and maneuvered to exhibit aerial feats of different degrees of difficulty.
Kites generally fall into two broad categories: those that are flown with a single string and those flown with two strings affixed to the kite. A variety of single-string kites are well-known, including the Chinese kite, barrel kite, Malay kite, Marconi-jib kite and Indian-fighter kite. While there are significant differences in the wind speed single-string kites can be flown at, as well as the type of maneuvers each can perform, it is generally true that they perform best in low to moderate winds and are incapable of exhibiting radical maneuvers such as direct overhead flight and dramatic turns accompanied by nearly parallel flight to the ground. Because of the limited weather conditions and limited maneuverability in which single-string kites can be flown, two-string kites that exhibit a wide range of desirable properties have been accepted among kite enthusiasts.
As is apparent from the name, a primary feature of two-string kites is the attachment of two strings of equal length to the kite, one to the right and left sides of the kite, respectively. By pulling on either of strings the kite enthusiast can put a two-string kite through exceptional maneuvers. Indeed, the maneuverability of two-string kites is due to constant adjustment of the tension on the string. When tension is applied to either the right or left string, the kite responds by moving in the corresponding direction. If tension is continuously applied evenly on one string, the kite turns continuously in that direction. For example, a clockwise spin is imparted to the kite by pulling in on the right string and stopped by subsequently pulling in on the left string. Be exerting even tension on both lines after a particular line of flight is established, the direction of flight can be maintained. Thus, a variety of aerial maneuvers can be performed by the sequence in which the operator pulls on the right and left strings.
A feature that distinguished single-string from dual-string kites is the flight angle of attack. Single-string kites fly at a substantially fixed angle of attack to the ground, whereas dual-string kites exhibit a variable angle of attack. When the angle of attack is great, a dual-sting kite is capable of obtaining high speeds and performing rapid turns.
Several dual-string kites are presently commercially available with names that adequately describe their aerial maneuverability, for example Sky Cat, Sky-Ro-Gyro and Super Stuntor.
In my copending U.S. patent application Ser. No. 07/073,996 and its parent application Ser. No. 06/804,778, I have described and claimed a steerable two-string kite suitable for sailing in variable winds. This kite contains flexible support members for adjusting the curvature of its sail during flight in reaction to the force of the wind so as to enhance its maneuverability. Its ability to adjust curvature of the sail allows this kite to perform many flying maneuvers in a manner superior to previous kites. These include maintaining constant speed over a wide range of angles relative to the ground, direct overhead flight and 90-degree turns relative to the center of the kite, all without the need to adjust or alter the position of the strings affixed to the kite. The superiority of this prior kite has been established in a number of professional kite flying competitions which competitors using this kite have won.
It has been found with the prior kite that it is usually advantageous to maintain the sail curvature under a variety of wind and flight conditions. However, with the structure of the prior kite that has not always been possible. For instance, in right wind conditions, the force of the wind on the kite may not be sufficient to cause the curvature of the sail to develop. A similar challenge exists when the flight path of the kite is parallel to the wind direction, as in direct overhead or 90-degree positions relative to the kite flyer. Under such conditions, the maneuverability of the kite is found to decrease. Typically it is found that the sail begins to flutter, causing the kite to lose stability, turn over and float to the ground.
The problem cannot be overcome by simply forming the sail into a curved shape with a rigid brace, for that prevents the sail from varying its curvature under different wind conditions, which is of course an important feature of the kite. It would therefore be of significance to have a kite structure which would retain the advantageous ability to vary curvature as my prior kite can, but which would also allow the sail to retain the varying curvatures and not lose its shape during flying.